I would, which is kind of the point.

So do you mean horror? Because looking at your top 50 games you have several Zelda games above Luigi's Mansion 3.

Oh, boy, do I like this concept!

Hard to say if I am honest.  I think that is what makes LM special.  It doesn't fit in a standard genre.  I'm not sure what it is.  I view Zelda as adventure.  LM is more action/horror/puzzle.  I lean mostly towards puzzle than anything.  For me LM isn't the same genre as Zelda.  Granted Zelda is always puzzle heavy.  I find genres hard to define in modern gaming.  Pikmin is one of my favorites as well, again not sure what genre that is.  Resource management?

A lot of interesting games suggested in this thread like 'sacrifice' :)

I'll just add one that didnt sell, it's probably the most detailed and accurate sim of evolution, but with some really fascinating strategy gameplay

Evolution: The Game of Intelligent Life (1997) is a life simulation and real-time strategy game that allows players to experience, guide, and control evolution from an isometric view on either historical earth or on randomly generated worlds while racing against computer opponents to reach the top of the evolution chain, and gradually evolving the player's animals to reach the "grand goal of intelligent life"

Pikmin is pretty well defined, RTS, real time strategy. Generally Zelda and LM are both considered Action-Adventure.

 Omega Boost & Bulk Slash are probably the best 3D Mech action games I played in the 32 bit era. I know AC was born from that generation and honestly don't think they were that great until PS2 generation. Omega Boost on a pure technical level is above Bulk Slash. Both are great games of the era tho and while Bulk Slash does have a cult following. It now has a full english patch with voice acting. Me and one of the leads on that project follow one another on twitter. Had some fun BS streams. Omega Boost needs more love tho.

You realise you're arguing against opinions right? :P 

I definitely wouldn't put Zelda in the same genre as Luigi's Mansion, nor would I lump Pikmin into a general RTS genre. Both those games were pretty much unique when they came out.

As for the topic, difficult question, as the apex is a tall order for a hidden gem. Not sure if it would qualify, but for me, Celeste not only has great gameplay, but the way the story intertwines with the platforming is amazing. It was critically very wel received, but only sold roughly 1 million as far as I can find.

For an indie game. 1 million is a massive success plus won awards at the Game Awards.

Well, yeh, but but compared to some other platformers sales, it doesn't come close.